This background section provides a context for the disclosure. The description herein may include concepts that could be pursued but are not necessarily ones that have been previously conceived or pursued. The description is not intended to be limiting and unless otherwise stated, nothing in this section is admitted as prior art simply by inclusion in this section.
The migration of broadcasting services, such as cable television and multimedia-on-demand, to packet-oriented networks as well as the embracing of emerging applications, such as teleconferencing and storage networks by the Internet, place significant traffic demands on the Internet. To keep up with such bandwidth demand, packet switches and routers need to provide efficient multicast switching and packet replication.
The forwarding of packets in the Internet depends on the switching efficiency of routers and switches. Presently, there are different buffering strategies to build packet switches. Input buffered (IB) switches provide limited throughput and require complex scheduling schemes. Output buffered (OB) switches offer high throughput but require infeasible memory speedup. Combined input crosspoint buffered (CICB) switches deliver better switching performance than input buffered switches, but the memory amount in the buffered crossbar is large (the number of crosspoint buffers equals N2, where N is the number of ports).
In addition to the high performance of CICB packet switches under unicast traffic, the crosspoint buffers in these switches help to provide call splitting intrinsically. Different from IB switches, CICB switches do not require cell transmission after inputs and outputs have been matched. In CICB switches, one input can send up to one (multicast) cell to the crossbar, and one or more cells destined to a single output port can be forwarded from multiple inputs to the crossbar at the same time slot. Therefore, CICB switches have natural properties favorable for multicast switching as contending copies for a single output can be sent to the crosspoint buffers from several inputs at the same time slot without blocking each other.
Existing packet switches mostly target unicast traffic. It is expected that in the near future multicast and broadcast services will demand most of the available bandwidth of the Internet. Current packet switches provide limited services for multicast traffic. CICB switches are seen as the promising architecture for building efficient switches. However, multicast packets can easily exhaust the available internal buffers in current CICB switches. Handling and management of multicast traffic by switches and routers can become very expensive as the sheer amount and speed of memory necessary often becomes cost prohibitive if not simply infeasible. To lower the cost of memory implementation, the required memory amount should be reduced or kept to a minimum while keeping high efficiency in packet switching and replication.